Blacksmith Forge Made From the Bathroom Sink

The sweltering heat had finally moved on and Giant Tick season was coming to a close (not kidding, they are HUGE here), when I decided to fire up my hacked together blacksmith forge made out of an old bathroom sink and aquarium stand.

In the age-old formula I needed to supply an air source to a fuel to create enough heat to make iron malleable. I got the idea that this particular bathroom sink might be a good candidate for a fire bowl after I banged my shin with it and then cursed at it. It was clearly made of cast iron and as proof it was clearly unfazed by my tirade of words which I hope my son has learned from the Internet and not from listening to me remodel the bathroom.

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From Gates to FPGA’s – Part 1: Basic Logic

It’s time to do a series on logic including things such as programmable logic, state machines, and the lesser known demons such as switching hazards. It is best to start at the beginning — but even experts will enjoy this refresher and might even learn a trick or two. I’ll start with logic symbols, alternate symbols, small Boolean truth tables and some oddball things that we can do with basic logic. The narrative version is found in the video, with a full reference laid out in the rest of this post.


1The most simple piece of logic is inversion; making a high change to low or a low change to high. Shown are a couple of ways to write an inversion including the ubiquitous “bubble” that we can apply almost anywhere to imply an inversion or a “True Low”. If it was a one it is now a zero, where it was a low it is now a high, and where it was true it is now untrue.


2Moving on to the AND gate we see a simple truth table, also known as a Boolean Table, where it describes the function of “A AND B”. This is also our first opportunity to see the application of an alternate symbol. In this case a “low OR a low yields a low”


3Most if not all of the standard logic blocks come in an inverted form also such as the NAND gate shown here. The ability to invert logic functions is so useful in real life that I probably used at least three times the number of NAND gates as regular AND gates when doing medium or larger system design. The useful inversion can occur as spares or in line with the logic.

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Weekend Proves Hardware Wins Hackathons

Teams hacking on hardware won big this weekend in New York. There were ten teams that answered Hackaday’s call as we hosted the first ever hardware hackathon at the Tech Crunch Disrupt NYC. These teams were thrown into the mix with all of the software hackers TC was hosting and rose to the top. Eight out of our ten teams won!

As we suspected, having something physical to show off is a huge bonus compared to those showing apps and webpages alone. Recipe for awesome: Mix in the huge talent pool brought by the hardware hackers participating, then season with a dash of experience from mentors like [Kenji Larson], [Johngineer], [Bil Herd], [Chris Gammell], and many more.

Out of over 100 teams, first runner-up went to PicoRico, which built a data collection system for the suspension of a mountain bike. The Twillio prize went to Stove Top Sensor for Paranoid, Stubburn Older Parents which adds cellphone and web connectivity to the stove, letting you check if you remembered to turn off the burns. The charismatic duo of fifteen-year-olds [Kristopher] and [Ilan] stole the show with their demonstration of Follow Plants which gives your produce a social media presence which you can then follow.

We recorded video and got the gritty details from everyone building hardware during the 20-hour frenzy. We’ll be sharing those stories throughout the week so make sure to check back!

VCF East: [Bil Herd] And System Architecture

Last Friday the Vintage Computer Festival was filled up with more than a dozen talks, too many for any one person to attend. We did, however, check out [Bil Herd]’s talk on system architecture, or as he likes to call it, the art and science of performance through balance. That’s an hour and fifteen minute talk there; coffee and popcorn protocols apply.

The main focus of this talk is how to design a system from the ground up, without any assumed hardware, or any specific peripherals. It all starts out with a CPU, some memory (it doesn’t matter which type), and some I/O. That’s all you need, whether you’re designing a microwave oven or a supercomputer.

The CPU for a system can be anything from a 6502 for something simple, a vector processor for doing loads of math, or have a RISC, streaming, pipelined, SIMD architecture. This choice will influence the decision of what kind of memory to use, whether it’s static or dynamic, and whether it’s big or little endian. Yes, even [Bil] is still trying to wrap his head around endianness.

MMUs, I/O chips, teletypes, character displays like the 6845, and the ANTIC, VIC, and GTIA make the cut before [Bil] mentions putting the entire system together. It’s not just a matter of connecting address and data pins and seeing the entire system run. There’s interrupts, RTCs, bus arbitration, DTACK, RAS, and CAS to take care of that. That will take several more talks to cover, but you can see the one last Friday below.

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How to Build a Thermocouple Amplifier

A Thermocouple is a terrific way to measure temperature. The effects of temperature change on dissimilar metals produces a measurable voltage. But to make that measurement you need an amplifier circuit designed for the thermocouple being used.

Linear Technology LTC 1049 Low Power Zero-Drift Operational Amplifier with Internal Capacitors
Linear Technology LTC 1049 Low Power Zero-Drift Operational Amplifier
with Internal Capacitors

While researching “Zero Drift Amplifiers” as a follow-up to my video on Instrumentation Amplifiers I noticed the little schematic the front page of the LTC1049 datasheet which is shown here. I thought it was an ideal example of an analog application where some gain and some “gain helper” were needed to accomplish our useful little application of amplifying a thermocouple probe.

In the video I don’t really talk much about the thermocouples themselves other than the type I see most of the time which is type K. If you’re not already familiar with the construction of these probes you can find an informative write-up on thermocouples and the different types on the Wikipedia page and you might also want to check out the Analog Devices app note if you would like to know more. What I will cover is a reliable and precise way to read from these probes, seen in the video below and the remainder of the post after the break.

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We Assume Control: SPI and a Digital Potentiometer

In the last video I demonstrated a Universal Active Filter that I could adjust with a dual-gang potentiometer, here I replace the potentiometer with a processor controlled solid-state potentiometer. For those that are too young to remember, we used to say “solid-state” to differentiate between that and something that used vacuum tubes… mostly we meant you could drop it without it breakage.

The most common way to control the everyday peripheral chips available is through use of one of the common Serial Protocols such as I2C and SPI.  In the before-time back when we had only 8 bits and were lucky if 7 of them worked, we used to have to memory map a peripheral or Input/Output (I/O) controller which means we had to take many control and data lines from the microprocessor such as Data, Address, Read/Write, system clocks and several other signals just to write to a couple of control registers buried in a chip.

Nowadays there is a proliferation of microcontrollers that tend to have built-in serial interface capability it is pretty straightforward to control a full range of peripheral functions; digital and analog alike.  Rather than map each peripheral using said data and address lines,which is a very parallel approach,  the controller communicates with peripherals serially using but a handful of signal lines such as serial data and clock. A major task of old system design, mapping of I/O and peripherals, is no longer needed.

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Universal Active Filters: Part 2

An easy way to conceptualize active filters is thinking about audio speakers. A speaker crossover has a low-pass, high-pass and band-pass effect breaking a signal into three components based upon frequency. In the previous part of this series I took that idea and applied it to a Universal Active Filter built with a single chip opamp based chip known as the UAF-42. By the way, it’s pretty much an older expensive chip, just one I picked out for demonstration.

Using a dual-ganged potentiometer, I was able to adjust the point at which frequencies are allowed to pass or be rejected. We could display this behavior by sweeping the circuit with my sweep frequency function generator which rapidly changes the frequency from low to high while we watch what can get through the filter.

In this installment I’ll test the theory that filtering out the harmonics which make up a square wave results in a predictable degradation of the waveform until at last it is a sine wave. This sine wave occurs at the fundamental frequency of the original square wave. Here’s the video but stick with me after the break to walk through each concept covered.

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